Agilent Technologies HP 8719D Service Manual page 289

Analog Bus Nodes
The following paragraphs describe the 23 analog bus nodes. They are listed
in numerical order and are grouped by assembly. Refer to the "Overall Block
Diagram" for node locations.
Press (
USER PRESET
then use the front panel keys or knob to select an analog bus node. Terminate
the entry by pressing (ZJ
1. + 0.37V (+ 0.37 V reference)
Check for a flat line at approximately +0.37V. This is used as the voltage
reference in the Analog Bus Correction Constants adjustment for calibrating
out the analog bus high/low resolution gain and offset errors. The absolute
voltage level is not critical, but it should be the same in high and low
resolution.
2. + 2.5OV (+ 2.50 V reference)
Check for a flat line at approximately + 2.5V. This voltage is used in the
Analog Bus Correction Constants adjustment as a reference for calibrating
the analog bus low resolution circuitry.
3. Aux Input
(Rear panel input)
This selects the rear panel AUX INPUT to drive the analog bus for making
voltage and frequency measurements. It can be used to look at test points
within the instrument on the CRT (using the CRT as an oscilloscope).
Connect the test point of interest to the AUX INPUT BNC connector on the
rear panel. This feature can be useful if an oscilloscope is not available.
Also, it can be used for testing voltage-controlled devices by connecting
the driving voltage of the DUT to the AUX IN connector. You can look
at the driving voltage on one display channel while displaying the DUT
S-parameter response on the other display channel.
With A?% ~&l'E. turned ON, you can examin e analog bus nodes with external
equipment (see &.l% %J.!lO; on QFF under the "Analog Bus Menu" heading).
See "HP-1B Service Mnemonic Definitions" for HP-IB considerations.
4. (Ground reference)
1 O-30 Service Key Menus and Error Messages
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